Channel architectures are almost universally found in complex natural and synthetic systems. Channels existing as waveguides, particle guides, and circuits and are found in both raised and recessed forms. Although channels can be used for theoretical illustrations, such as a channel capacity in an information system, channels are practical solutions for efficiently routing physical particles such as electrons, ions, molecules, protons, etc. from a source to a destination.
Channels that are reduced in size can be classified as microchannels when they range from 1 μm to 1000 μm. Within this micro range, the physical phenomena of mechanical, electrical, optical and fluidic circuitry have variable optical size, performance and cost features. For example, microfluidic circuits below 30 μm used for fluid transport on chips and microreactors, have significant resistance to flow and require more exacting particle filtration while at the same time only yielding moderate dividends in chip real estate. In addition to the increased flow resistance, at sub 30 μm dimensions, there is an increased cost for finer dimensional control. In contrast, electrical circuits yield increased performance with smaller dimensions and warrant the increased cost associated with their manufacture. However, even electrical circuits have applications, for example, in packaging, where channel sizes are micron to millimeter in scale.
Prior art methods of forming microchannel patterns for mechanical, electrical, optical and fluidic circuitry include: embossing, imprinting, soft lithography, inkjet and laser direct writing, and a variety of photolithography techniques. By far the most popular techniques known in the art have employed some form of photolithography to create highly defined, desired microchannel features. However, to date, most of these photolithographic procedures involve multi-step mask and developing steps, thus making processing labor intensive and expensive.
Methods are known in the art for using etchants to treat the surface of a polymer substrate. However, these methods do not teach or suggest the formation of microchannels or channel-like structures that are effective in establishing electrical, optical and fluidic circuitry. Surface preparation methods are known in the art utilizing surface etchants, in low concentrations, as a method of surface roughening to permit subsequent metal lamination in the fabrication process. These methods do not teach or suggest the formation of channels or channel-like structures effective in establishing electrical, optical and fluidic circuitry. Only minimal roughening of the polymer surface utilizing chemical etchants is achieved by the methods previously known in the art.
Additional methods are known in the art utilizing etchants to form through-holes and voids in the substrate for eventual circuit board patterning. These methods do not teach or suggest the use of an etchant system to form complex channels and fluid pathways necessary for the construction of an operational microfluidic device.
The methods known in the art utilizing etchants to produce incidental features in the substrate do not result in the formation of effective grooved patterns and fluid conduits in the substrate that are continuous patterns that can be used in the subsequent formation of microfluidic devices. Although the vias and holes are formed using masking techniques known in the art, these methods do not teach or suggest a method for connecting these features together in a continuous pattern necessary to provide fluid transport.
While various means for the etching of polymer surfaces are known in the art, the current state of the art does not teach or suggest the formation of complex channel structures and other fluidic canals necessary to fabricate microfluidic devices. In contrast, the techniques known the art describe the formation of rough surfaces for further treatment or formation of holes through the polymer substrate. In addition, all of these features are intermediate in nature, and provide little function, and do not contribute to the development of a functional pathway for the fabrication of micofluidic devices.
Accordingly, what is needed in the art is a method for the direct patterning of channels in different photoreactive materials using an electronic mask to create a variety of electrical and photonic circuits, mechanical acoustic waveguides, RF waveguides, and gas or liquid flow channels.